### Using context managers in dependencies with `yield` { #using-context-managers-in-dependencies-with-yield }

/// warning

This is, more or less, an "advanced" idea.

If you are just starting with **FastAPI** you might want to skip it for now.

///

  /**
   * Returns a new target iterator each time it's called. This is the iterator you are trying to
   * test. This must return an Iterator that returns the expected elements passed to the constructor
   * in the given order. Warning: it is not enough to simply pull multiple iterators from the same
   * source Iterable, unless that Iterator is unmodifiable.
   */
  protected abstract I newTargetIterator();

  /**

 *       {@link #verifyNotNull(Object)} and {@link Preconditions#checkNotNull(Object)} perform the
 *       same function with more clarity.
 * </ul>
 *
 * <h3>Warning about performance</h3>
 *
 * <p>Remember that parameter values for message construction must all be computed eagerly, and
 * autoboxing and varargs array creation may happen as well, even when the verification succeeds and

      return constructor.newInstance();
    } catch (InstantiationException | IllegalAccessException impossible) {
      throw new AssertionError(impossible);
    } catch (InvocationTargetException e) {
      logger.log(Level.WARNING, "Exception while invoking default constructor.", e.getCause());
      return arbitraryConstantInstanceOrNull(type);
    }
  }

  private static <T> @Nullable T arbitraryConstantInstanceOrNull(Class<T> type) {

作用域是更精密的权限系统，遵循 OAuth2 标准，与 OpenAPI 应用（和 API 自动文档）集成。

OAuth2 也是脸书、谷歌、GitHub、微软、推特等第三方身份验证应用使用的机制。这些身份验证应用在用户登录应用时使用 OAuth2 提供指定权限。

脸书、谷歌、GitHub、微软、推特就是 OAuth2 作用域登录。

本章介绍如何在 **FastAPI** 应用中使用 OAuth2 作用域管理验证与授权。

/// warning | 警告

本章内容较难，刚接触 FastAPI 的新手可以跳过。

OAuth2 作用域不是必需的，没有它，您也可以处理身份验证与授权。

但 OAuth2 作用域与 API（通过 OpenAPI）及 API 文档集成地更好。

不管怎么说，**FastAPI** 支持在代码中使用作用域或其它安全/授权需求项。

很多情况下，OAuth2 作用域就像一把牛刀。

Exatamente como queríamos. ✔️

Isso porque o FastAPI usa esse `root_path` para criar o `server` padrão no OpenAPI com o URL fornecido pelo `root_path`.

## Servidores adicionais { #additional-servers }

/// warning | Atenção

Este é um caso de uso mais avançado. Sinta-se à vontade para pular.

///

Por padrão, o **FastAPI** criará um `server` no OpenAPI schema com o URL para o `root_path`.

   * null, null, null]} regardless of the true comparison order of those three values (which might
   * not even implement {@link Comparable} at all).
   *
   * <p><b>Warning:</b> by definition, this comparator is not <i>consistent with equals</i> (as
   * defined {@linkplain Comparator here}). Avoid its use in APIs, such as {@link
   * TreeSet#TreeSet(Comparator)}, where such consistency is expected.

Именно как и хотелось. ✔️

Это потому, что FastAPI использует `root_path`, чтобы создать в OpenAPI сервер по умолчанию с URL из `root_path`.

## Дополнительные серверы { #additional-servers }

/// warning | Предупреждение

Это более продвинутый сценарий. Можно пропустить.

///

По умолчанию FastAPI создаёт в схеме OpenAPI `server` с URL из `root_path`.

  /**
   * Returns a new target iterator each time it's called. This is the iterator you are trying to
   * test. This must return an Iterator that returns the expected elements passed to the constructor
   * in the given order. Warning: it is not enough to simply pull multiple iterators from the same
   * source Iterable, unless that Iterator is unmodifiable.
   */
  protected abstract I newTargetIterator();

  /**

Dies liegt daran, dass FastAPI diesen `root_path` verwendet, um den Default-`server` in OpenAPI mit der von `root_path` bereitgestellten URL zu erstellen.

## Zusätzliche Server { #additional-servers }

/// warning | Achtung

Dies ist ein fortgeschrittener Anwendungsfall. Überspringen Sie das gerne.

///

Standardmäßig erstellt **FastAPI** einen `server` im OpenAPI-Schema mit der URL für den `root_path`.